JP2018015716A - Denitrification system and denitrification method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a denitrification technology capable of denitrifying gas containing nitrogen oxide without using ammonia as a reducer.SOLUTION: A denitrification system 10 includes a NO oxidation system 15 having inside a catalyst cartridge 16 having an oxidation catalyst for accelerating oxidation of nitrogen monoxide, for oxidizing nitrogen monoxide contained in gas into nitrogen dioxide, and a NOabsorption part 18 for allowing inflow of gas oxidized in the NO oxidation system 15, and allowing absorbent to absorb nitrogen dioxide contained in exhaust gas.SELECTED DRAWING: Figure 1

Description

  Embodiments of the present invention relate to a denitration technique for removing nitrite oxide from exhaust gas containing nitrite oxide.

  The exhaust gas discharged from the gas turbine in the power generation facility contains nitrogen oxides (NOx). From the viewpoint of environmental conservation, the NOx emission concentration to the atmosphere is regulated, so it is necessary to remove NOx contained in the exhaust gas.

  In thermal power plants where combined cycle power generation is performed, as a method for removing NOx contained in exhaust gas, there is a wide range of denitration methods that make NOx in exhaust gas harmless to nitrogen and water vapor by a selective catalytic reduction reaction using ammonia as a reducing agent. It is used.

  In recent years, power generated by renewable energy such as photovoltaic power generation has been incorporated into the power grid, and in order to cope with fluctuations in power supply and demand according to renewable energy, output adjustment is performed by performing non-rated operation different from normal rated operation. It is carried out.

JP-A-6-31136

  When a non-rated operation associated with output adjustment is performed at a thermal power plant, the concentration of NOx contained in the exhaust gas changes and the ratio of NO / NOx (the ratio of NO to NOx) in the exhaust gas varies. Therefore, it becomes difficult to adjust the supply amount of ammonia in accordance with the NOx concentration and the NO / NOx ratio.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a denitration technique capable of denitrating a gas containing a noble oxide without using ammonia as a reducing agent.

A denitration system according to an embodiment of the present invention includes a NO oxidation apparatus provided in a flow path through which a gas containing nitrogen monoxide flows, and a catalyst cartridge that promotes an oxidation reaction that oxidizes nitric oxide to nitrogen dioxide. And a NO ₂ absorption section that is provided downstream of the NO oxidation device in the flow path and holds an absorption liquid that absorbs nitrogen dioxide.

  A denitration method according to an embodiment of the present invention includes a step of passing a gas through a NO oxidation apparatus including a catalyst cartridge having an oxidation catalyst that promotes oxidation of nitric oxide, and the NO oxidation in an absorption liquid that absorbs nitrogen dioxide. Passing the gas after passing through the apparatus.

  According to the embodiment of the present invention, it is possible to provide a denitration technique capable of denitrating a gas containing a nitrite oxide without using ammonia as a reducing agent.

The block diagram which shows the structure of the thermal power plant to which the denitration system which concerns on this embodiment was applied. The NOx-containing gas simulating an exhaust gas, in the case of using an oxidizing catalyst to the catalyst reaction in the present embodiment, a graph showing the concentration of NOx in the exhaust gas (NO and NO ₂₎ before and after the reaction. (A) The figure which shows the structural example of the NO oxidation apparatus in this embodiment, (B) Sectional drawing of AA. (A) In NO oxidation apparatus, explanatory drawing when catalyst cartridges are arranged in five stages, (B) explanatory diagram when catalyst cartridges are arranged in three stages. The block diagram which shows the structure of the thermal power plant to which the modification of the denitration system which concerns on this embodiment was applied. The flowchart which shows an example of the denitration method which concerns on this embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a diagram showing a configuration of a denitration system 10 according to the present embodiment. Here, a case where the denitration system 10 is applied to a thermal power plant using a combined cycle power generation method will be described as an example.

  In the combined cycle power generation method, gas turbine power generation that generates power by rotating the gas turbine with the energy generated when the volume of the combustion gas expands by burning fuel such as LNG, and the high-temperature exhaust gas emitted from the gas turbine are regenerated. This is a high-efficiency power generation method combined with steam power generation that generates power by rotating a steam turbine with steam generated by use.

  Specifically, the gas turbine 11 guides air compressed using a compressor to a combustor, and continuously burns fuel to generate high-temperature and high-pressure gas. This gas is expanded by a turbine to obtain rotational energy. The obtained rotational energy is transmitted to the generator 12 to generate electric power.

  On the other hand, high-temperature exhaust gas (usually 300 ° C. or higher) discharged from the gas turbine 11 is guided to the exhaust heat recovery boiler 13 via the first flue 50. The exhaust heat recovery boiler 13 is provided with a water pipe 14 into which the circulating water flows, so that the circulating water in the water pipe 14 exchanges heat with the exhaust gas flowing into the boiler and changes to steam. The water pipe 14 in the exhaust heat recovery boiler 13 is bent and formed into a wave shape, thereby increasing the contact area with the exhaust gas.

  The steam generated in the exhaust heat recovery boiler 13 is sent to the steam turbine to rotate the steam turbine. And the obtained rotational energy is transmitted to the generator for steam turbines, and electric power is generated. The steam after rotating the steam turbine is returned to water by the condenser and sent to the exhaust heat recovery boiler 13.

The denitration system 10 of this embodiment applied to such a thermal power plant is equipped with a catalyst cartridge 16 having an oxidation catalyst that promotes oxidation of NO inside, and flows exhaust gas discharged from the gas turbine 11 into it. , and NO oxidation apparatus 15 for oxidizing NO contained in the exhaust gas to NO _2, and flows the exhaust gas after being oxidized in the NO oxidation apparatus 15, NO ₂ absorption unit for absorbing the NO ₂ contained in the exhaust gas in the absorbing solution 18.

  Although FIG. 1 shows the case where the denitration system 10 is applied to a combined cycle power generation type thermal power plant, this embodiment can also be applied to a general gas turbine power generation method. In this case, the exhaust heat recovery boiler 13 is omitted, and the exhaust gas discharged from the gas turbine 11 is directly input to the NO oxidation device 15.

The NO oxidation device 15 includes a plate-like catalyst cartridge 16 that uses an oxidation catalyst that promotes oxidation of NO as a constituent material or that is coated with an oxidation catalyst.
The catalyst cartridge 16 is formed in a honeycomb shape or the like so that the exhaust gas can flow therethrough. For example, the inside of the NO oxidation device 15 is partitioned in a direction orthogonal to the flow direction of the exhaust gas (the direction of the arrow in FIG. 1). Are arranged as follows.

  As the oxidation catalyst, a metal containing silver and ruthenium or a catalyst supporting a metal oxide is used with an aluminum oxide as a carrier. This oxidation catalyst is thermally stable and has the property of promoting the oxidation reaction of NO under a high temperature environment of 250 ° C. or higher. In order to promote the oxidation function of the catalyst, it is desirable that the content of silver and ruthenium with respect to the aluminum oxide is adjusted to about 0.5 to 5%.

  As an oxidation catalyst, at least one of platinum, palladium, copper, nickel, palladium, cobalt, rhodium, and iron with respect to at least one carrier of cerium oxide, titanium oxide, and magnesium oxide. A catalyst supporting two metals or metal oxides may be used.

The exhaust gas discharged from the exhaust heat recovery boiler 13 and flowing into the NO oxidation device 15 through the second flue 51 undergoes an oxidation reaction represented by the following formula (1) by the action of the oxidation catalyst of the catalyst cartridge 16. Thus, NO contained in the exhaust gas is oxidized into NO _2.

2NO + O ₂ → 2NO ₂ (1)

  Note that the oxidation catalyst of the catalyst cartridge 16 exhibits an oxidation function when the temperature of the exhaust gas in contact with the catalyst cartridge 16 is about 250 ° C. or higher. Therefore, it is desirable that high-temperature exhaust gas flow into the NO oxidation device 15. On the other hand, if the NO oxidation device 15 is installed in front of the water pipe 14 that performs heat recovery in the exhaust heat recovery boiler 13, the exhaust heat recovery efficiency decreases due to heat loss due to the catalyst cartridge 16. For this reason, about arrangement | positioning of the NO oxidation apparatus 15, it is desirable to shorten the 2nd flue 51 and to provide immediately after the exhaust heat recovery boiler 13. FIG. Further, the exhaust heat recovery boiler 13 and the NO oxidizer 15 may be integrated, and in this case, the NO oxidizer 15 is arranged immediately after the water pipe 14.

  Further, in order to maintain the inside of the NO oxidation device 15 at a high temperature of 250 ° C. or higher, a heater for heating the inside of the NO oxidation device 15 may be provided.

Here, the oxidation performance of the oxidation catalyst according to the present embodiment will be described using a specific evaluation example. FIG. 2 is a graph showing the concentration of NOx (NO and NO ₂ ) in the exhaust gas before and after the reaction when a NOx-containing gas simulating the exhaust gas is subjected to a catalytic reaction using the oxidation catalyst in the present embodiment.

  In this evaluation example, an aluminum oxide containing silver and ruthenium is used as an oxidation catalyst, and the catalytic reaction is performed in a high temperature environment of about 300 ° C. in order to simulate the temperature inside the NO oxidation device 15.

As a reaction gas, the composition of exhaust gas having a high NO ratio was simulated, and 200 ppm NOx (NO ₂ / NOx ratio = 0) + simulated combustion air (16% O ₂ + 84% N ₂ ) was set. In addition, 200 ppm NOx means the upper limit of the NOx concentration assumed in a general thermal power plant.

  An evaluation apparatus for evaluating the oxidation performance of a catalyst inputs a reaction gas preparation unit that generates a reaction gas using a gas cylinder, a reaction gas heating unit that heats the reaction gas to a predetermined temperature, and a sample of an oxidation catalyst It comprises a catalyst layer and a gas analyzer that collects exhaust gas after passing through the catalyst layer and analyzes the NOx concentration.

First, in the reaction gas preparation unit, NO / N ₂ , O ₂ , and N ₂ gas supplied from a gas cylinder are mixed using a static mixer to generate a reaction gas. The produced reaction gas is heated to the reaction temperature (around 300 ° C.) in the reaction gas heating section. And the exhaust gas after a heating is sent to a catalyst layer.

  The reaction gas reaching the catalyst layer was controlled so that the flow rate was 3.5 L / min with a mass flow controller by measuring the flow rate using a float type flow meter. The amount of catalyst was 10 g, and the space velocity was about 19000 (1 / h). Further, thermometers were installed on the downstream side of the reaction gas heating section and the catalyst layer, and it was confirmed that the reaction temperature was reached.

The exhaust gas that has passed through the catalyst layer is discharged after the NOx concentration is measured in the gas analysis unit. For the concentration analysis in the gas analyzer, a gas detector tube manufactured by GASTEC for NO and NO ₂ separation measurement was used.

As shown in FIG. 2, the NOx concentration, which was 200 ppm (NO: 200 ppm + NO ₂ : 0 ppm) before the catalyst was charged, became 95 ppm (NO: 5 ppm + NO ₂ : 90 ppm) after the catalyst was charged. From this result, it was found that even when the NO ratio in NOx is 100%, the NO oxidation function works effectively and the NO oxidation reaction shown in the above formula (1) proceeds.

Subsequently, the configuration of the NO oxidation device 15 will be described with reference to FIG. FIG. 3B is a cross-sectional view taken along the line AA of FIG. Here, a case where five catalyst cartridges 16 (16 _{1 to} 16 ₅ ) are arranged inside the NO oxidation device 15 will be described as an example.

  The NO oxidation device 15 includes a gas flow space 54 in which exhaust gas flowing in through the second flue 51 flows in the direction of the chimney 17, a storage portion 55 that is provided on the side of the device and stores each of the catalyst cartridges 16, It has. When the catalyst cartridge 16 is stored in the storage unit 55, the catalyst cartridge 16 may be taken out of the apparatus from the storage unit 55 and replaced with a new cartridge.

The catalyst cartridges 16 _{1 to} 16 ₅ are arranged in parallel along the flow direction of the exhaust gas so that the exhaust gas sequentially flows.

  Each of the catalyst cartridges 16 is composed of two cartridges that can be separated at the central position of the gas flow space 54. Each of the two cartridges moves up and down between the gas flow space 54 and the storage space 56 of the storage portion 55.

  When the catalyst cartridge 16 is disposed in the gas flow space 54, the two cartridges are inserted into the gas flow space 54 to form a one-stage catalyst cartridge 16. On the other hand, when not arranged in the gas flow space 54, the two cartridges are pulled out to the side of the apparatus and stored in the storage unit 55. Note that the catalyst cartridge 16 is inserted into and removed from the gas flow space 54 by a drive mechanism using a hydraulic cylinder, a pneumatic cylinder, a ball screw, or the like.

  As described above, by enabling the catalyst cartridge 16 to be taken in and out of the gas flow space 54 in which the exhaust gas flows, the amount of the catalyst arranged for oxidizing NO can be adjusted. In the present embodiment, the single-stage catalyst cartridge 16 is configured by using two cartridges, but the single-stage catalyst cartridge 16 may be configured by a single cartridge.

Returning to FIG. 1, a method for adjusting the amount of the catalyst to be arranged will be described.
The 1st measurement part 22 measures the density | concentration of NO contained in waste gas using the measurement sensor (illustration omitted) provided in the 1st flue 50 where the waste gas discharged | emitted from the gas turbine 11 flows. The first measurement unit 22 may measure the concentrations of NO, NO ₂ , and NOx. The first measurement unit 22 transmits the acquired measurement data to the catalyst amount adjustment unit 23.

  The catalyst amount adjusting unit 23 adjusts the number of catalyst cartridges 16 arranged inside the NO oxidation device 15 (gas flow space 54) according to the concentration of NO contained in the exhaust gas measured by the first measuring unit 22. .

Specifically, the concentration of NO that can be oxidized by one catalyst cartridge 16 is obtained, and the catalyst cartridge 16 necessary for oxidizing NO contained in the exhaust gas into NO ₂ based on the measured concentration of NO. Determine the number. And the catalyst cartridge 16 arrange | positioned in the NO oxidation apparatus 15 is changed so that it may become the determined number. The catalyst cartridge 16 to be arranged may be adjusted according to the ratio of NO concentration to NOx concentration in exhaust gas (NO / NOx).

FIG. 4 is a diagram for explaining an arrangement example of the catalyst cartridge 16 that is adjusted according to the NO concentration. FIG. 4A shows that five catalyst cartridges 16 are required to oxidize NO in the exhaust gas to NO ₂ by the catalyst amount adjustment unit 23, and the catalyst cartridges 16 are placed in five stages in the NO oxidation device 15. The case where it arranges is shown. On the other hand, in FIG. 4B, since the NO concentration is lower than in the case of FIG. 4A, the catalyst amount adjusting unit 23 determines that the three catalyst cartridges 16 can oxidize, and the NO oxidation device 15 receives the catalyst cartridge. 16 shows a case where 16 are arranged in three stages.

  Note that the catalyst cartridge 16 positioned on the exhaust gas input side is highly consumed. For this reason, it is good also as a structure which preferentially accommodates the catalyst cartridge 16 located in the input side of exhaust gas after progress of a fixed use period.

  In this way, by adjusting the catalyst cartridge 16 arranged, the operation output is adjusted at the thermal power plant, and even when the NO concentration in the exhaust gas discharged from the gas turbine 11 fluctuates, it is optimal. A simple oxidation catalyst can always be placed in the NO oxidizer 15. Thereby, the pressure loss accompanying the arrangement of the catalyst cartridge 16 can be minimized while maintaining the NO oxidation efficiency.

Returning to FIG. 1, the description will be continued.
The exhaust gas after NO is oxidized to NO ₂ in the NO oxidation device 15 is guided to the inside of the chimney 17 via the third flue 52 connected to the chimney 17. At the uppermost part of the chimney 17, an exhaust port for discharging exhaust gas to the atmosphere is provided.

Inside the chimney 17, a NO ₂ absorber 18 and an eliminator 19 are provided in order along the direction in which the exhaust gas flowing into the chimney 17 flows to the exhaust port at the top of the chimney. An absorption liquid holding tank 20 that holds the absorption liquid is provided at the lowermost portion in the chimney 17.

The NO ₂ absorption unit 18 flows in the exhaust gas discharged from the NO oxidizer 15 and causes the absorption liquid to absorb NO ₂ contained in the exhaust gas. The NO ₂ absorption unit 18 is configured by spraying an absorption liquid on a honeycomb-like main body through which exhaust gas can flow.

The absorbent is sucked from the absorbent holding tank 20 using the supply pump 21 and supplied to the NO ₂ absorber 18. The absorbing liquid holding tank 20 by placing directly under the NO ₂ absorbent portion 18, the absorbing liquid falling from NO ₂ absorption unit 18 is collected in absorption liquid holding tank 20 can be reused.

The absorbing liquid is applicable as long as it absorbs NO ₂ , and water may be used, or a tertiary amine aqueous solution such as methyldiethanolamine (MDEA) or triethanolamine (TEA) may be used. .

The absorption liquid adjustment unit 25 adjusts the supply amount of the absorption liquid supplied to the NO ₂ absorption unit 18 according to the NOx concentration measured by the first measurement unit 22. Specifically, from the NOx concentration in the exhaust gas discharged from the gas turbine 11, the NO ₂ contained in the exhaust gas after being exhausted from the NO oxidizer 15 (after NO in the exhaust gas is oxidized to NO ₂ ). Determine the concentration. Then, an absorption liquid necessary for absorbing this concentration of NO ₂ is supplied to the NO ₂ absorption unit 18 via the supply pump 21.

Further, the absorption liquid controller 25, the concentration of NO ₂ contained in exhaust gas discharged from the NO ₂ absorbent portion 18 is measured by the second measuring unit 24, depending on the concentration of NO ₂ measured NO ₂ absorption section 18 You may adjust the supply amount of the absorption liquid supplied to. The second measurement unit 24 measures the concentration of NO ₂ contained in the exhaust gas using a measurement sensor (not shown) provided in the flow path in the chimney 17 through which the exhaust gas discharged from the NO ₂ absorption unit 18 flows. It is a measuring instrument.

Eliminator 19 is a metal filter for adsorbing and removing NO _2, after passing through the NO ₂ absorption unit 18, the NO ₂ remaining in the exhaust gas is removed. The exhaust gas from which NO ₂ has been removed by the eliminator 19 is discharged into the atmosphere from the exhaust port of the chimney 17.

As described above, in the present embodiment, by oxidizing NO in the exhaust gas in the NO oxidation unit 15 having an oxidation catalyst to NO _2, is removed by absorbing the NO ₂ in the exhaust gas in the absorption liquid. Thereby, it is possible to denitrate exhaust gas in a wet manner without using ammonia as a reducing agent. Since ammonia is not used, it is not affected by regulation due to ammonia leak, flue, and pressure loss due to ammonium sulfate adhesion inside the pipe, which were problems in the conventional denitration method using selective catalytic reduction.

Further, in the thermal power plant, when adjusting the operation output according to the supply and demand fluctuation caused by using the electric power from the renewable energy, the NOx concentration in the exhaust gas discharged from the gas turbine 11 is 20 to 200 ppm, NO _{The 2} / NOx ratio varies in the range of 0-1. In the present embodiment, NO in the exhaust gas is oxidized to NO ₂ by the NO oxidation device 15 and NO ₂ is removed by the absorbing solution, so that the exhaust gas can be denitrated without being affected by the NOx concentration. Furthermore, in the combined cycle power generation system that uses exhaust heat, it is not necessary to provide a denitration system in the exhaust heat recovery boiler 13, so that the exhaust heat recovery of the exhaust heat recovery boiler 13 can be performed efficiently.

  FIG. 5 is a configuration diagram showing a configuration of a thermal power plant to which a modified example of the denitration system 10 according to the present embodiment is applied. 5 that have the same configuration or function as those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

In the present modification, the NO ₂ absorber 18 holds the absorbing liquid in the holding tank, and the open end of the third flue 52 that guides the exhaust gas discharged from the NO oxidizer 15 to the chimney 17 is the absorbing liquid. Opened inside. For this reason, the exhaust gas discharged | emitted from the NO oxidation apparatus 15 is sent directly in absorption liquid. Thus, it is possible to improve the absorption efficiency of NO ₂ to the absorbing solution.

  FIG. 6 is a flowchart showing an example of the denitration method according to the present embodiment (see FIG. 1 as appropriate).

  The exhaust gas output from the gas turbine 11 flows into the exhaust heat recovery boiler 13 (S10). In the exhaust heat recovery boiler 13, heat exchange occurs between the high-temperature exhaust gas that has flowed in and the circulating water flowing in the water pipe 14, and steam is generated (S11). The exhaust gas discharged from the exhaust heat recovery boiler 13 is sent to the NO oxidation device 15.

In the NO oxidation device 15, NO contained in the exhaust gas is oxidized to NO ₂ by the catalyst cartridge 16 having an oxidation catalyst (S12). The exhaust gas oxidized to NO ₂ is sent to the chimney 17.

The NO ₂ absorbing portion 18 of the chimney 17 causes the absorbing liquid to absorb NO ₂ contained in the exhaust gas (S13). Then, the exhaust gas from which NO ₂ has been removed is discharged from the exhaust port of the chimney 17 (S14).

According to the denitration system in the embodiment described above, the NO in the exhaust gas is oxidized to NO ₂ in the NO oxidation unit having an oxidation catalyst is removed by absorbing the NO ₂ in the exhaust gas in the absorption liquid. Thereby, exhaust gas can be denitrated without using ammonia as a reducing agent.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.
For example, in the description of the embodiment, the denitration target gas is the exhaust gas output from the gas turbine 11, but the denitration target gas is not limited thereto. Any gas containing nitric oxide can be a target for denitration.

10 ... denitration system, 11 ... gas turbine, 12 ... generator, 13 ... exhaust heat recovery boiler, 14 ... water pipe, 15 ... NO oxidizer, 16 ... catalyst cartridge, 17 ... chimney, 18 ... NO ₂ absorption part, 19 ... Eliminator, 20 ... Absorbing liquid holding tank, 21 ... Supply pump, 22 ... First measuring section, 23 ... Catalyst amount adjusting section, 24 ... Second measuring section, 25 ... Absorbing liquid adjusting section, 50 ... First flue, 51 2nd flue, 52 ... 3rd flue, 54 ... Gas flow space, 55 ... Storage part, 56 ... Storage space.

Claims (9)

A NO oxidizer provided in a flow path through which a gas containing nitrogen monoxide flows and having a catalyst cartridge inside for promoting an oxidation reaction for oxidizing nitric oxide to nitrogen dioxide;
A denitration system comprising: a NO ₂ absorption unit that is provided downstream of the NO oxidation device in the flow path and holds an absorption liquid that absorbs nitrogen dioxide.   2. The denitration system according to claim 1, wherein the catalyst cartridge contains a metal containing silver and ruthenium or a catalyst containing a metal oxide as a component with respect to an aluminum oxide support.   The denitration system according to claim 1 or 2, wherein a temperature of the gas in contact with the catalyst cartridge is 250 ° C or higher. The NO oxidation apparatus includes a plurality of the catalyst cartridges,
The plurality of catalyst cartridges are disposed along the flow direction of the gas so that the gas sequentially passes through the plurality of catalyst cartridges,
4. The denitration system according to claim 1, wherein each of the catalyst cartridges is provided so as to be able to be put in and out of a gas flow space in which the gas flows in the NO oxidation apparatus. A first measuring unit for measuring the concentration of nitric oxide contained in the gas;
The denitration system according to claim 4, further comprising: a catalyst amount adjusting unit that adjusts the amount of the catalyst cartridge disposed in the gas flow space according to the measured concentration of nitric oxide. The gas is exhaust gas discharged from a gas turbine of a thermal power plant,
Claims 1 to 5 comprising an absorbing liquid adjustment unit that adjusts a supply amount of the absorption liquid supplied to the NO ₂ absorbent portion according to the concentration of nitrogen oxides contained in the exhaust gas discharged from the gas turbine The denitration system according to any one of the above. A second measurement unit that measures the concentration of nitrogen dioxide contained in the gas that has passed through the NO ₂ absorption unit;
The denitration system according to any one of claims 1 to 6, further comprising an absorption liquid adjustment unit that adjusts a supply amount of the absorption liquid supplied to the NO ₂ absorption unit according to the measured concentration of nitrogen dioxide. . The gas is exhaust gas discharged from a gas turbine of a thermal power plant,
An exhaust heat recovery boiler that recovers exhaust heat of the exhaust gas and generates steam,
The denitration system according to any one of claims 1 to 7, wherein the NO oxidation device is provided immediately after a water pipe that collects exhaust heat inside the exhaust heat recovery boiler. Passing the gas through a NO oxidizer comprising a catalyst cartridge having an oxidation catalyst that promotes oxidation of nitric oxide;
Passing the gas after passing through the NO oxidizer through an absorption liquid that absorbs nitrogen dioxide, and a denitration method.

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